i965/batch: avoid reverting batch buffer if saved state is an empty

There's no point reverting to the last saved point if that save point is
the empty batch, we will just repeat ourselves.

CC: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: 3faf56ffbd "intel: Add an interface for saving/restoring
                     the batchbuffer state."
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107626
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i965/brw_compute.c

@@ -167,7 +167,7 @@ static void
 brw_dispatch_compute_common(struct gl_context *ctx)
 {
    struct brw_context *brw = brw_context(ctx);
-   bool fail_next = false;
+   bool fail_next;
 
    if (!_mesa_check_conditional_render(ctx))
       return;
@@ -185,6 +185,7 @@ brw_dispatch_compute_common(struct gl_context *ctx)
    intel_batchbuffer_require_space(brw, 600);
    brw_require_statebuffer_space(brw, 2500);
    intel_batchbuffer_save_state(brw);
+   fail_next = intel_batchbuffer_saved_state_is_empty(brw);
 
  retry:
    brw->batch.no_wrap = true;

src/mesa/drivers/dri/i965/brw_draw.c

@@ -885,7 +885,7 @@ brw_draw_single_prim(struct gl_context *ctx,
 {
    struct brw_context *brw = brw_context(ctx);
    const struct gen_device_info *devinfo = &brw->screen->devinfo;
-   bool fail_next = false;
+   bool fail_next;
 
    /* Flag BRW_NEW_DRAW_CALL on every draw.  This allows us to have
     * atoms that happen on every draw call.
@@ -898,6 +898,7 @@ brw_draw_single_prim(struct gl_context *ctx,
    intel_batchbuffer_require_space(brw, 1500);
    brw_require_statebuffer_space(brw, 2400);
    intel_batchbuffer_save_state(brw);
+   fail_next = intel_batchbuffer_saved_state_is_empty(brw);
 
    if (brw->num_instances != prim->num_instances ||
        brw->basevertex != prim->basevertex ||

src/mesa/drivers/dri/i965/genX_blorp_exec.c

@@ -268,7 +268,7 @@ genX(blorp_exec)(struct blorp_batch *batch,
    assert(batch->blorp->driver_ctx == batch->driver_batch);
    struct brw_context *brw = batch->driver_batch;
    struct gl_context *ctx = &brw->ctx;
-   bool check_aperture_failed_once = false;
+   bool check_aperture_failed_once;
 
 #if GEN_GEN >= 11
    /* The PIPE_CONTROL command description says:
@@ -309,6 +309,7 @@ retry:
    intel_batchbuffer_require_space(brw, 1400);
    brw_require_statebuffer_space(brw, 600);
    intel_batchbuffer_save_state(brw);
+   check_aperture_failed_once = intel_batchbuffer_saved_state_is_empty(brw);
    brw->batch.no_wrap = true;
 
 #if GEN_GEN == 6

src/mesa/drivers/dri/i965/intel_batchbuffer.c

@@ -299,6 +299,13 @@ intel_batchbuffer_save_state(struct brw_context *brw)
    brw->batch.saved.exec_count = brw->batch.exec_count;
 }
 
+bool
+intel_batchbuffer_saved_state_is_empty(struct brw_context *brw)
+{
+   struct intel_batchbuffer *batch = &brw->batch;
+   return (batch->saved.map_next == batch->batch.map);
+}
+
 void
 intel_batchbuffer_reset_to_saved(struct brw_context *brw)
 {

src/mesa/drivers/dri/i965/intel_batchbuffer.h

@@ -24,6 +24,7 @@ struct intel_batchbuffer;
 void intel_batchbuffer_init(struct brw_context *brw);
 void intel_batchbuffer_free(struct intel_batchbuffer *batch);
 void intel_batchbuffer_save_state(struct brw_context *brw);
+bool intel_batchbuffer_saved_state_is_empty(struct brw_context *brw);
 void intel_batchbuffer_reset_to_saved(struct brw_context *brw);
 void intel_batchbuffer_require_space(struct brw_context *brw, GLuint sz);
 int _intel_batchbuffer_flush_fence(struct brw_context *brw,